Ultrasensitive fluorescent sensing platform based on N, Zr co-doped carbon dots: Cr(VI) detection and solid-state...

By modulating the nitrogen precursor (ethylenediamine vs. urea), we tailored the ratio of graphitic N to amino N in N, Zr co-doped carbon dots, thereby enabling the construction of an ultrasensitive fluorescent probe for Cr(VI) detection with an exceptionally low detection limit of 2.208 μM. Furthermore, real-time fluorescent visualization of latent fingerprints was successfully achieved. Systematic characterization revealed that ethylenediamine-derived carbon dots (CDs-2), possessing a significantly higher content of graphitic nitrogen, exhibited a distinct electron-deficient structure. Compared with CDs-1, which has a relatively lower graphite nitrogen content, the photoluminescence (PL) intensity of CDs-2 is significantly enhanced. The specific recognition of Cr(VI) was attributed to a synergistic quenching mechanism, predominantly static quenching accompanied by dynamic quenching and the inner filter effect, with excellent anti-interference capability. Additionally, the synthesized CDs-2@MOF composite exhibited a core-shell morphology, blue-shifted PL emission, and novel surface defect states. This hybrid material demonstrated dual functionality in both latent fingerprint development and light-emitting diodes encapsulation. This work highlights a defect engineering strategy in carbon dots governed by the graphitic N/amino N ratio, providing novel perspectives for the development of multifunctional fluorescence probes.